The transportation of solids over long distance by slurry pipeline has been applied to a wide range of materials, including coal, iron ore, limestone, phosphate and numerous other minerals. With regards to coal transportation, it has been a tendency in many countries to build power generating stations in the environs of the mine itself and to transmit the resulting output of energy by high voltage transmission lines. As will be appreciated, use of a slurry pipeline would permit the power station to be sited wherever desired. Studies have indicated that, as an alternative to rail transit of coal or to mine mouth generating plants, slurry pipelining is the least expensive option.
However, the conventional slurry pipeline technology has some disadvantages in that preparation of a fine coal/water slurry at the mine site, as well as coal separation at the terminal, impacts the unit transportation cost, setting the lower limit of competitiveness with alternative transportation modes for low annual tonnage and short distance.
The use of lump coal in a coal/water slurry proved to be feasible but was found to require high pumping power and resulted in excessive wear of the pipeline. U.S. Pat. Nos. 2791471, 3073652 and 4685840 provide good examples of prior art coal/water slurry transport.
To eliminate, or at least minimize, rapid settling and so reduce wear and required pumping power it was realized that a slurry vehicle of a density similar to that of the lump coal was highly desirable. Several kinds of slurry composition have been proposed. U.S. Pat. Nos. 3,637,263 and 3,719,397 disclose coal slurry transport using a magnetite/water vehicle; In particular U.S. Pat. No. 3,637,263 teaches the use of two compositions of slurry, coal fines and water on the one hand and coarse coal, magnetite and water on the other hand. U.S. Pat. No. 4,721,420 discloses the transportation of coarse coal particles in a dense liquid carbon dioxide vehicle.